Chicken erythrocyte mononucleosomes in 1 nM ionic strength buffer were studied as a function of temperature using quasielastic light scattering (QLS), sedimentation velocity, conductivity and fluorescence methods. Two relaxation times were observed when an electronic filter with a low frequency cut-off of 0.3 Hz was used in the QLS study. The slow time was electronically filtered out with a filter having a low frequency cut-off of 150 Hz (fast track data). The effective Stokes radius below 5 degrees C was calculated to approximately 54 Angstrom units at these temperatures in 10 mM ionic strength. Our data suggest a "two-state" conformational model as a function of ionic strength, which is in agreement with recent transient electric dichroism studies of Crothers' group. The effective Stokes radius in 1 mM ionic strength was observed to increase from 64 Angstrom units to approximately 209 Angstrom units at 35 degrees C. This increase is attributed to increased electrostatic friction and not as a conformation change. Conductivity measurements in this temperature range suggest counterions are absorbed. Fluorescence increment calculations show quenching below 30 degrees C which abruptly changes to enhancement above 30 degrees C. This "transition" temperature coincides with circular dichroism studies reported by Weischet et al. (Nucl. Acids Res., 5 (1978) 139) and is not associated with thermal denaturation of the core particle.